M. Tully has given me an excuse to write about social contract theory by mentioning it in a comment to an earlier post.
I have to agree with Alonzo and Ron. But, I base it on social contract theory (I'm still not sure there are many conflicts between that and DU).
So, let me account for some of the differences between social contract theory and desire utilitarianism.
Objection 1: There is no social contract. Any moral argument built on a false premise is unsound by definition. The premises for an argument must be true, and the inferences drawn from them must be valid, for the argument to count as sound. Basing any moral conclusions on the myth of the social contract, like basing moral conclusions on the myth of a benevolent God or an impartial observer, is just doomed to failure from the start.
Response 1: Social contract theorists would respond to this by saying something like, "Of course there is no real social contract. The social contract is a metaphor – like when your science teacher in Jr. High School asked you to think of electrons in an atom as having orbits, like planets around the sun, with each orbit representing an energy level."
Answer 1: A metaphor for what? We can't judge a metaphor to be accurate or inaccurate until we know what it is we are metaphoring. If the 'social contract' is just a pedagogical tool – something we can use to help people grasp more complex concepts – then what are those more complex concepts being captured by the metaphor? Whatever they are, that is our moral theory. Then we can ask to what degree the metaphor of the social contract actually captures this truth.
Response 2: The term 'social contract' refers to a hypothetical entity. Assume you can get everybody in the world into a room to agree to a contract. Everybody must sign. The ‘social contract’ is the term that refers to the hypothetical compromise social contract that you can get everybody to sign.
Answer 2a: First, the assumption that there is a compromise contract that everybody will have reason to sign is false. Every contract will have some group who has more and stronger reason to bow out than to sign on. Altering the contract to give them reason to sign on, will give somebody else reason to bow out. We need some evidence that there is a contract that everybody would have reason to sign, even hypothetically.
Answer 2b: Even assuming that there is a contract for everybody to sign, as I sit here ready to act, what reason do I have to consider the terms of such a hypothetical contract? My interaction is with real people in the real world having real beliefs and desires. Even though they might have reason to sign this hypothetical contract, they are not likely to actually be thinking in terms of such a contract. Why must I go outside of this set of real-world facts in order to make my decision?
Objection 2: Social contract theory ignores the vital concern with how to motivate people to abide by the terms of the contract. The social contract is, ultimately, a set of rules telling agents what they may or may not do. However, people have no capacity to simply pick a rule and act on it. People always act so as to fulfill the most and strongest of their desires (given their beliefs). If an act that conforms to a social contract rule also happens to fulfill the most and strongest of the agent's desires given her beliefs, then he will obey the contract. If the two diverge, then the agent will violate the contract. This means that the contract, in order to be effective, has to define what fulfills the most and strongest desires of all agents.
I do not think that social contract theory has an answer to this objection. You simply cannot come up with a set of policies that has the property of being such as to fulfill the most and strongest of all peoples’ desires. So, it is not possible to devise a contract that is actually effective.
Desire utilitarianism actually has a great deal in common with social contract theory. It captures, I think, much of what seems to be promising in social contract theory – without the contract, and without the disconnect from agents' motivations.
For example, social contract theory defines a right act as the act that conforms to the terms of a social contract that everybody would sign.
Desire utilitarianism defines the right act as the act that a person with good desires would perform – where good desires are those desires that people generally have reason to promote.
Imagine people in a social contract setting, only they are not trying to pick out a set of rules that go into a contract, but desires that everybody will adopt (or will avoid). It looks at the love of truth and determines that there is a reason for everybody to acquire a love of truth. It looks at a desire to rape and correctly determines that this is a desire to be inhibited.
'Right acts', in this case, are simply those acts that people with good desires would perform. There is no problem with motivating agents with good desires into doing the right acts – they will already have the desires that would be fulfilled by those actions.
As for the question of how we motivate agents into acquiring good desires – we use praise, condemnation, reward, and punishment. More generally, we use the tools of social pressure to promote those desires we have the most and strongest reason to promote, and to inhibit those desires that we have the most and strongest reason to inhibit.
The motivation to promote good desires and inhibit bad desires, in turn, comes from the desires that good desires will help to fulfill, and the desires that bad desires would thwart.
There is no actual contract – not even a hypothetical contract. There are, instead, 'terms' that take the form of desires that people generally have reason to promote or inhibit.
There is no problem with linking right acts to motivation, because the right act is the act that a person with good desires would perform.
Why does a person acquire good desires? It is because others use social tools such as praise, condemnation, reward, and punishment to promote those desires (and to inhibit bad desires).
What reason do we have to use social tools to promote good desires and inhibit bad desires? Since good desires are desires that tend to fulfill other desires, and bad desires are desires that tend to thwart other desires, this gives us our reason for using social tools to promote good desires and inhibit bad desires.
No social contract is necessary – yet, the theory results in some elements that we find in social contract theory. It is still the case, in a sense, that moral principles are those that people generally have reason to support – that people generally would agree to put into a social contract, if there were one. The major difference is that desire utilitarianism also evaluates the reasons for supporting various rules (the quality of the desires that go into supporting or rejecting rules), and explains the link between the rules and motives of agents.